The following invention relates generally to single dose syringe and its method of use. More specifically, it relates to a blister syringe having an integral needle with a sheath having a break-zone, with an optional integrity indicator, guard fingers, and secondary prep blister.
There is a need for an inexpensive syringe that may be conveniently manufactured and preloaded with a single dose of injectable fluid. Preferably, such a syringe should be unitary and self-contained, comprising all of the elements needed for performing an injection. In addition, such a syringe would preferably have a built-in safety element in order to reduce the chance of accidental needle sticks and the transfer of blood-borne pathogens such as AIDS and hepatitis. Such a safety element should function automatically. Another desirable safety element would be an indicator to insure the integrity of the preloaded dose.
The present invention provides a unitary syringe having a mounted needle surrounded by a sheath having a break-zone. The fluid medicament to be injected is contained within a blister cavity formed between upper and lower polymeric layers, and is in fluid communication with the needle. It is preferred that the blister cavity be fully filled with the fluid, and substantially free of non-dissolved gas. The sheath may be formed from the same upper and lower polymeric layers forming the blister cavity, or it may be supplied as a pre-form with the needle.
The syringe may be manufactured as a single unit, but it is preferred that the syringe be formed as an array, generally a linear array, held together by tabs, or preferably by a thinned web of at least one of the polymeric layers. The web should be thin enough to be easily torn or broken by the user. Typically, a twisting motion would be used to separate an individual syringe from an array of syringes.
The polymeric layer comprises one or more polymeric lamina. A sealable lamina may be used with a barrier lamina, for instance. Such multilayer polymeric constructions are well known. Polymers that may be used for the polymeric barrier layer include ethylene/vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC) and polyacrylonitrile (PAN). These polymers are exemplary only, and any polymeric or other flexible material may be used as a barrier consistent with the stability of the medicament, the storage time required, compatibility with the medicament, and any other particular requirements. While polymeric barrier lamina or layers are preferred, the film may be metallized with aluminum or other metals to improve the barrier properties, however, it is preferred that the optical depth of the metallized coating does not prevent visual inspection of the contents. Exemplary polymers that may serve as sealable lamina, and in some cases as a barrier also, are polyethelene, polypropylene, polycarbonate, nylon, polyester, PVC, EVA and copolymers and blends of the above. Any other suitable heat sealable polymer may be used.
Filling of the blister cavity by way of a fill canal is preformed from the needle (distal) end of the syringe, or from the blister (proximal) end. A plug is inserted into the fill canal or, preferably, the walls of the canal are collapsed to seal off the syringe. In the latter case, sealing is preferably by application of ultrasonic pressure horn or pin. When an array of syringes is formed, the blister cavities may be gang filled from a central port via runners to the fill canals, with the runners later trimmed and discarded. Preferably, a vacuum is drawn to collapse the blisters, and the fill fluid is then introduced under pressure.
The integrity of the blister cavity can be assured by an optional indicator in at least one of the layers forming the blister walls. Such an indicator would typically be molded with an outer concave surface. When filled with an internal cavity pressure greater than atmospheric, the indicator would invert, becoming convex. Breaking the break-zone of the sheath or any other communication of the cavity with the environment would allow leakage of the fluid resulting in the indicator returning to its favored molded convex form. It is preferred that the indicator be placed generally in the center of the blister wall to provide a tactile indication to the user.
Accidental needle sticks can be reduced by optional guard fingers surrounding the needle. These fingers extend past the distal (sharpened) end of the needle, and substantially lie in a first plane (the syringe plane) with the needle tip. The tips of the fingers make first contact with the target surface to be injected. The user then directs the syringe in a second plane (the injection plane, substantially perpendicular to the syringe plane) whereby the finger guards are flexibly and reversibly bent, allowing the needle tip to encounter the target surface. The user then directs the syringe forward along the axis of the needle to insert the needle into the target surface. A xe2x80x9cZxe2x80x9d motion is transcribed by the needle tip during the insertion process.
Injection of the fluid is performed by squeezing the blister between two fingers, generally the thumb and index fingers. Optionally, the first wall of the blister cavity may be made bistable, with the second wall more rigid, so that upon inversion of the first wall the first wall closely fits the mating second wall, thereby driving most of the fluid from the cavity.
A syringe may comprise a second blister cavity (sans sharpened needle) for application of an injection prep such as alcohol or other sterilizing fluid. In this way, everything needed for the injection is self-contained in a unitary syringe. The second blister cavity need not be fully filled.
It is an object of the present invention, therefore, to provide a single dose fully sealed syringe comprising a needle having an integral sheath having a break-zone, wherein the needle is in fluid communication with a blister cavity formed between a first and a second layer, and wherein at least one of the layers is flexible.
It is another object of at least one embodiment of the present invention to provide an array of single dose fully sealed syringes, joined by separable webs or tabs.
It is another object of at least one embodiment of the present invention to provide a single dose safety syringe having guard fingers extending past the needle tip.
It is another object of at least one embodiment of the present invention to provide a single dose fully sealed syringe having an integrity indicator on a wall of a blister cavity containing an injectable fluid medicament.